The present invention relates generally to coin operated devices, and particularly to electronic coin acceptors for testing the acceptability of coins.
The trend of our society toward replacement of mechanisms with solid-state devices has failed to produce a widely-used electronic coin accepting device for less complex vending and coin operated machines. While some machines in more demanding service use rather costly and elaborate electronic coin handling systems, the majority of coin operated machinery, such as video or arcade games, laundry machines and most dispensing machines, still rely on mechanical means of verifying or rejecting coins.
The standard mechanical acceptors, which typically contain delicately balanced pivoting members and magnets, are notorious for their susceptability to jamming. They are often limited to the acceptance of a single denomination of coin, and must be replaced with a different mechanism to allow acceptance of any other coin denomination. Furthermore, they are unable to distinguish between some coins of differing value, and between some coins and slugs. Attempts to supplant these mechanical units with simple, electronic acceptors have largely failed, due to reasons including the failure of the units to hold calibration, to reject slugs, or to compete with the cost of mechanical units. Additionally, more complex, but reliable electronic acceptor units have not proven cost-effective in simpler vending applications.
The method of coin discrimination employed most commonly by electronic coin acceptors is inductive coupling. The coin under test is caused to pass within the proximity of an inductive coil or element which is part of a frequency selective LC (inductor-capacitor) circuit. The characteristics of the LC circuit are affected by inductive coupling between the coil and the coin. Specifically, the coin causes a change in the loss characteristics and inductance of the coil. A certain degree of change in the these parameters is typical of a given type of coin. By suitable means of measurement of such changes, an identification of the coin can be accomplished. This method of coin discrimination is superior to other means (mechanical or electro-optical) in that it is non-contacting and is unaffected by non-metallic contamination. Another class of electromagnetic discrimination, variable reluctance, offers some of the same advantages, but due to the small size of the signal induced by coins moving at practical speeds, requires extreme amplification. This approach is vulnerable to internally and externally generated noise, both electrical and magnetic, and requires extensive shielding.
Inductive coupling of a coil with a coin as a means of discrimination of coins is the most practical method, but is not without problems. The inductive coil used for coin sensing and the LC circuit of which it is part must be extremely stable with temperature and time to allow adequate coin discrimination, as the changes induced in the circuit by a given coin may be only very slightly different from those caused by some other coin. Moreover, the auxiliary circuitry required to measure and compare the characteristics of the LC circuit to values of the characteristics typical of the given coin must also exhibit high stability (e.g., low temperature, humidity and aging coefficient). Using standard, manufacturable methods of electronic design, these demands can only marginally be met; this accounts, in part, for the failure of prior art to achieve the required coin discriminating power while giving adequate reliability freedom from loss of calibration.
The most successful solution used in prior art to this problem is to use multiple tests, each of lower accuracy. This allows more drift prior to loss of calibration, and discriminates coins by the logical ANDing of two or more tests. Further justification of this approach is the fact that a condition of the LC circuit that is characteristic of a given coin is not unique to that denomination, but may also be characteristic of some distinctly different coin subjected to the same, single test. This problem is compounded by the fact that coins, being a manufactured product, are subject to tolerances in diameter, thickness, composition, weight, and degree of stamped relief. Thus, there is not a single value of the characteristic of the LC circuit corresponding to the given coin, but a range of values of the characteristic. If a single test is used to distinguish coins, certain coins are indiscernable from other coins due to overlapping of their respective ranges of values of the LC circuit characteristic. However, if the coin under test is subjected to a variety of tests, coins indistinguishable by one test may be distinguished by another. This has been done in prior art by subjecting the coin under test to two or more complete tests, implemented in largely independent, separate and parallel circuits. This achieves the desired discrimination, but the multiplying of circuitry hardware increases the cost, complexity, and probability of electronic component failure.
Prior art inductive coin acceptors generally fall into two groups: oscillator-based units and transmitter receiver (TR)-based units. Either approach relies on the inductive coupling between coils and coins.
Oscillator-based units contain a coil which couples inductively with coins under test and which comprises a portion of an LC circuit (or tank circuit). The LC circuit is driven by an AC signal, typically a sine wave or some portion of a sine wave. The tank circuit has a characteristic loss that is a function of frequency, and this loss falls to a minimum at a certain frequency. The tank circuit is driven by an active device that, in turn, receives its input from the tank circuit. This generalized oscillator operates as a closed loop, and is self-resonant at approximately the frequency of minimum loss of the LC tank circuit. When a coin couples with the coil it changes the apparent value of the coil's inductance, which changes the frequency of minimum loss of the tank circuit, and therefore, the frequency at which the circuit oscillates. The coin also affects the amount of loss of the LC tank, which causes a change in the amplitude of oscillation.
LC oscillator-based coin acceptors use one or the other of these two effects (frequency or amplitude changes) as the basis for discrimination of coins. But there are a number of problems associated with these oscillator-based devices. Unless very well shielded, an oscillator-based acceptor's coil shows excessive sensitivity to metal objects several inches away from the coil. Re-calibration after installation in a vending machine, may be required--and may be lost if background metal should move. Also, without extensive shielding, interference between adjacent coin acceptors (or other frequency sources) can cause amplitude or frequency modulation. Environmentally induced changes in oscillator component values cause both frequency and amplitude to vary from their initial calibrated states. Oscillator-based units that use amplitude to discriminate coins are especially prone to temperature drift problems because the DC resistance of the sensing coil is strongly affected by temperature; the amplitude of oscillation is a function of coil DC resistance, and will also vary. Another problem is that frequency of oscillation may be affected by variations in delay contributed by active components in the oscillator, which may also vary with temperature or time. Additionally, since an oscillator tank circuit is necessarily a rather high impedance circuit, a variation in the load placed on the tank circuit by ancillary components may affect amplitude.
TR-based circuits can be effective, but are necessarily more complex. Generally, a transmitting coil is driven at a given frequency and is inductively coupled to a receiving coil. The coin passes between the transmitting coil and receiving coil, affecting the phase and amplitude of the received signal. Discrimination is based upon either effect. Offering a potential advantage in the fact that the transmitting coil can be low impedance, and may be driven by a high-stable externally-generated source, this circuit can eliminate some problems common to LC oscillator-based circuits (through some prior designs fail to take advantage of this potential). Also, sensitivity to nearby metal and the chances of interference from other signal sources are reduced. Adjacent acceptors can be realized more easily. However, TR circuits are generally expensive due to the need for separate transmitting and receiving circuitry.
A principal objective of the present invention is to provide a low-cost electronic coin acceptor which also eliminates the reliability problems associated with previous acceptance means. No coin acceptor can be 100% jam-proof since there must be a slot for coins; anyone intent upon jamming the slot, surely can. However, the probability of failure during normal operation is greatly reduced in accordance with the present invention by the elimination of moving parts and fingers, magnets and mechanical switches.
Additionally, in accordance with the present invention the tendancy for an electronic coin acceptor to come out of adjustment is greatly reduced by providing the electronic coin acceptor with the capability of making automatic compensations. Once the electronic coin acceptor is programmed for a given coin, it will automatically adapt itself in order to continue to accept that type of coin. Hence, potential sources of degradation to the originally-programmed criteria for acceptance of the coin (such as change in value of electronic components, wear, or accumulation of dirt) are accommodated by the device.
While greater reliability is one of the most significant advantages of the present invention, the electronic coin acceptor is relatively inexpensive and still provides several unique and advantageous features. For example, as coins are examined by passing them through an electromagnetic field, it is not necessary to physically gauge coin size or material. Hence, the electronic coil acceptor does not contain hardware specifically designed to test one particular coin or size of coin, but may be used to test a broad range of coins with equal accuracy. Coins from the size of a U.S. dime to a U.S. half dollar may be accepted without any physical alterations being required. Another feature of the present invention is the ability not only to accept a wide variety of coin denominations, but also to be able to tally the values of the coins accepted. This ability may be used either to allow graduations of cost-per-item that were not possible previously in simple vending operations, or to allow the cost-per-item to be composed of combinations of small coin denominations.
Another objective of the present invention is to provide an electronic coin acceptor whose performance is essentially immune to temperature changes in active and passive components due to temperature, humidity, aging, etc.
A further objective of the present invention is to provide an electronic coin acceptor in which interference between propinquitous sensing elements is minimized so that two adjacent coin slots may be employed in the coin operated device.
It is an additional objective of the present invention to provide an electronic coin acceptor which will permit two or more separate tests for each acceptable coin denomination with no increase in the amount of circuitry over that required to conduct one test.
It is an additional objective of the present invention to provide an electronic coin acceptor which is capable of sensing the passage of a coin or other conductive object through the slot of the coin operated apparatus with the same circuitry required to determine the acceptability of the coin.
It is still another objective of the present invention to provide an electronic coin acceptor which is capable of automatically compensating for the degree of variability of each acceptable coin denomination.
It is yet another objective of the present invention to provide an electronic coin acceptor which is capable of eliminating variations in the way the coin is entered into the coin slot from affecting the performance of the acceptor.
It is a further objective of the present invention to provide an electronic coin acceptor which is capable of eliminating "string-fraud" or "wire fraud" on the coin operated apparatus.
It is still a further objective of the present invention to provide an electronic coin acceptor which need not be disassembled in order to be inspected.
It is yet a further objective of the present invention to provide an electronic coin acceptor which may quickly and easily be programmed to accept a plurality of coin denominations by an operator in the field without requiring a knowledge of computer programming, or requiring any special tools or a need to make any mechanical or electrical fine tuning adjustments.
To achieve the foregoing objectives, the present invention provides an electronic coin acceptor which generally comprises means for generating a driving signal having a selectively variable characteristic, means for controlling the selectively variable characteristic of the driving signal such that at least one predetermined testing characteristic for each coin denomination to be tested and accepted is selected for the driving signal in a predetermined sequence, means for creating an electromagnetic field in response to the driving signal and for producing an alternating signal which is responsive to an electrically conductive object in the presence of the electromagnetic field, means for detecting when the alternating signal crosses a predetermined threshold level and for producing a level detect signal indicative of the threshold crossing, and means for determining whether a conductive object in the presence of the electromagnetic field is an acceptable coin from the level detect signal. Preferably, the selectively variable characteristic of the driving signal is the frequency of the driving signal.
The present invention also provides a method of testing the acceptability of a coin which generally comprises the steps of providing at least one testing frequency for each coin denomination to be tested, creating an electromagnetic field utilizing the testing frequencies in a predetermined sequence, and measuring the effect upon the electromagnetic field when a conductive object is in the presence of the electromagnetic field, and determining whether a conductive object in the presence of said electromagnetic field is an acceptable coin from the changes in the electromagnetic field.
The present invention further provides a coin inspecting circuit which is capable of dynamically testing the acceptability of coins. This coin inspecting circuit generally comprises means for testing a conductive object to determine whether the conductive object is an acceptable coin in accordance with a predetermined coin acceptability criteria, means for determining whether the conductive object is an acceptable coin from the result of this test, and means for selectively altering the coin acceptability criteria for subsequent determination of coin acceptability in response to the result of this test.
Additional advantages and features of the present invention will become apparent from a reading of the detailed description of the preferred embodiments which makes reference to the following set of drawings in which: